The present invention relates to the field of mass-storage devices. More particularly, this invention relates to a method and ribbed shrouding spacer for flutter and windage losses reduction in 3.5xe2x80x3 form factor disc drives.
Devices that store data are key components of any computer system. Computer systems have many different types of devices where data can be stored. One common device for storing massive amounts of computer data is a disc drive. The basic parts of a disc drive are a disc assembly having at least one disc that is rotated, an actuator that moves a transducer to various locations over the rotating disc, and circuitry that is used to write and/or read data to and from the disc via the transducer. The disc drive also includes circuitry for encoding data so that it can be successfully retrieved from and written to the disc surface. A microprocessor controls most of the operations of the disc drive, in addition to passing the data back to the requesting computer and receiving data from a requesting computer for storing to the disc.
The disc drive includes a transducer head for writing data onto circular or spiral tracks in a magnetic layer the disc surfaces and for reading the data from the magnetic layer.
The transducer is typically placed on a small ceramic block, also referred to as a slider, that is aerodynamically designed so that it flies over the disc. The slider is passed over the disc in a transducing relationship with the disc. Most sliders have an air-bearing surface (xe2x80x9cABSxe2x80x9d) which includes rails and a cavity between the rails. When the disc rotates, air is dragged between the rails and the disc surface causing pressure, which forces the head away from the disc. At the same time, the air rushing past the cavity or depression in the air bearing surface produces a negative pressure area. The negative pressure or suction counteracts the pressure produced at the rails. The slider is also attached to a load spring which produces a force on the slider directed toward the disc surface. The various forces equilibrate so that the slider flies over the surface of the disc at a particular desired fly height. The air lubrication film eliminates the friction and resulting wear that would occur if the transducing head and disc were in mechanical contact during disc rotation. In some disc drives, the slider passes through a layer of lubricant rather than flying over the surface of the disc.
Information representative of data is stored on the surface of the storage disc. Disc-drive systems read and write information stored on tracks on storage discs. Transducers, in the form of read/write heads attached to the sliders, located on both sides of the storage disc, read and write information on the storage discs when the transducers are accurately positioned over one of the designated tracks on the surface of the storage disc. The transducer is also said to be moved to a target track. As the storage disc spins and the read/write head is accurately positioned above a target track, the read/write head can store data onto a track by writing information representative of data onto the storage disc. Similarly, reading data on a storage disc is accomplished by positioning the read/write head above a target track and reading the stored material on the storage disc. To write on or read from different tracks, the read/write head is moved radially across the tracks to a selected target track. The data is divided or grouped together on the tracks. In some disc drives, the tracks are a multiplicity of concentric circular tracks. Servo feedback information is used to accurately locate the transducer. The actuator assembly is moved to the required position and held very accurately during a read or write operation using the servo information.
When the disc assembly is rotated at high speed, the air adjacent to the spinning disc or discs is caused to move as well. This moving air moves between the rotating disc and the read/write transducer, creating an air bearing, and advantageously causing the transducer to xe2x80x9cflyxe2x80x9d over the disc surface. This moving air is thus a desirable feature of the disc drive.
The moving air from the disc or discs, as it passes by the transducer arm or arms and the fixed structures surrounding the disc assembly, also causes undesirable vibrations and windage losses in the disc drive, due to turbulence and/or friction. The flow disturbances/perturbations cause the disc(s) and/or transducers and transducer arms to vibrate, making precision tracking operations difficult. Windage losses cause more power to be consumed in rotating the disc(s). The windage losses and vibration increase dramatically with an increase in the speed of rotation of the discs in the disc drive. Currently, discs are rotated at 10,000-15,000 revolutions per minute in high performance disc drives. It is anticipated that rotational speeds will continue to climb in future products which will further magnify the problem. In addition, track density or the number of tracks per inch is also anticipated to increase since three is continued pressure to add capacity to disc drives. With thinner tracks, vibrations become more of a problem since tracking is also more difficult.
There is, therefore, a need for a method and structure for reducing flutter and windage losses in disc drives. There is also a need for a method and apparatus that will lessen vibration due to windage so that even more precise tracking can be accomplished.
A method and apparatus is described for reducing flutter and windage losses in disc drives. In one embodiment, a ribbed shroud is provided at the circumference of the disc assembly.
One aspect of the present invention provides a disc-drive system that includes a disc-drive housing, at least one disc mounted within the housing which rotates, a transducer having a read head positionable to read data from the disc, and a shroud structure near an outer circumference of the disc that reduces flutter and windage losses. In some embodiments, the shroud structure is ribbed.
Another aspect of the present invention provides a shroud structure for reducing flutter and windage losses in a disc drive. The structure includes a cylindrical section at a substantially constant first radius from an axis of the disc, the cylindrical section having one or more raised circumferential ribs depending on the number of discs, each having a top portion at a substantially constant second radius from the axis of the disc, the second radius being smaller than the first radius.
The present invention also provides a method for reducing flutter and windage losses in a disc drive. The method includes spacing a first shroud at each one of at least two different spacings from an outer-diameter edge of one or more discs within the disc drive. A performance characteristic of the disc drive is measured at each one of the at least two different spacings. The shroud spacings having the best performance characteristic is then selected.
In some embodiments, the performance characteristic measured by measuring step is spindle-motor current and in others the performance characteristic is off track read errors.
The present invention also includes a method for reducing flutter and windage losses in a disc drive. The method includes forming a ribbed structure spaced from and oriented opposite an outer-diameter edge of one or more discs within the disc drive. The ribs of the ribbed structure are oriented along a direction of rotation of the one or more discs.